diff -r f20373fcdde5 Lib/tempfile.py
--- a/Lib/tempfile.py	Thu May 05 14:34:35 2011 -0700
+++ b/Lib/tempfile.py	Fri May 06 01:45:08 2011 -0400
@@ -110,7 +110,7 @@
 
     _RandomNameSequence is an iterator."""
 
-    characters = "abcdefghijklmnopqrstuvwxyz0123456789_"
+    characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_"
 
     def __init__(self):
         self.rng = _Random()